Regarding an ink-jet recording head for recording an image by jetting fine droplets of ink, straightness of the flying course of ink droplets is strongly required for realizing the high quality image recording by constant stable ink jetting. When the ink adheres around the jetting nozzle, the course of the ink-jetted from the nozzle is deviated so that the straightness of the flying course of the ink droplets is lowered. Therefore, an ink repelling ability is provided onto the ink-ejecting surface of nozzle plate as the ink jetting surface by forming an ink-repellent layer so that the ink does not adhere around the jetting opening and the straightness of the ink flying course can be kept for ink jetting. As the ink repelling layer, a layer of fluororesin which is excellent in the ink repelling ability is usable, but the adhesiveness of such the fluororesin to the base material is low since the surface energy of the resin is low. When the adhesiveness to the base material is low, the ink repelling layer tends to be peeled off so that the stable jetting is hardly kept and the durability of the head is lowered.
So as to solve above problems, proposed is a method for improving the adhesiveness of a layer of fluororesin to the base material.
For example, disclosed is an ink-jet head which has an ink-repellent layer comprising fluorine containing polymer resin on a surface of orifice of inkjet head, provided thereon a structure having portion where perfluoro polyether chain or perfluoro alkyl chain bonds to (for example, Patent Document 1). According to the method described in Patent Document 1, ink-repellent layer which has high ink-repellency and abrasion resistance can be obtained. However, fluorine based solvent is necessary to form an ink-repellent layer and there exists issues in view of workability, environmental soundness or forming a uniform layer.
Further, disclosed is a production method of an inkjet recording head for forming ink-repellent layer on an ink jetting surface by using coating solution containing fluororesin aqueous dispersion and water-soluble polyamide-imide, and polyoxyethylene alkylether (for example, Patent Document 2). By the method described in Patent Document 2, an ink-repellent layer can be formed easily by using aqueous coating solution. Thus it exhibits excellent workability and environmental soundness and also in view of good adhesiveness to an ink-ejecting surface and realizing stable ejection, it has good performances. However, as the result of further investment by the applicant, it was found that it tends to form unevenness in formed ink-repellent layer and a slight variation in ejection performance, resulting in being necessary to further improvement.
Moreover, disclosed is an inkjet recording head having improved ejection stability in which amorphous resin having critical surface tension lower than 25 mN/m (for example, amorphous fluororesin having perfluoro polyether in main chain) bonds to nozzle plate base material through oxygen atom (for example, Patent Document 3). However, according to the method described in Patent Document 3, as well as a method described in Patent Document 1, non-aqueous solvent such as perfluorocarbon is required to form an ink-repellent layer and there exists issues in view of workability, environmental soundness or forming an uniform layer.
Further, disclosed is an inkjet head having improved ejection stability, ink repellency and abrasion resistance in which SiO2 layer containing SiO2 as main component is formed on ink jetting surface of a nozzle head, provided thereon ink-repellent layer formed by compound having alkoxy silane residue group bonded to a terminal of perfluoro polyether chain (for example, Patent Document 4). However, by the method described in Patent Document 4, in order to form an ink-repellent layer, productivity is low due to necessity of plural process. Furthermore, formed ink-repellent layer does not have enough adhesiveness to the base material and abrasion resistance.